The present invention refers to a procedure for the recovery of catalysts and adsorbent materials, such as active carbon, by means of thermal desorption. The active carbon is an adsorbent with a high adsorption capacity versus a great variety of substances, due to which it has numerous industrial applications. During the adsorption process, the retention capacity of the carbon diminishes, until it is converted into a "depleted carbon", The regeneration of depleted carbons is of great economic interest, since it facilitates its recycling. Said regeneration mainly consists in the desorption of adsorbed substances and thus restoring the adsorption power of the carbon.
Numerous carbon regeneration procedures exist, though only a few are used at industrial level. Among these, the following may be mentioned: Thermal, biological; water vapour regeneration; extraction with solvents; extraction with supercritical CO.sub.2 ; and wet oxidation.
In the thermal regeneration, the depleted carbon is subjected to a progressive and controlled heating, passing through successive stages: a) drying (water evaporation at 100.degree. C.); b) thermal desorption (desorption of volatile compounds 100-260.degree. C.): c) pyrolysis and carbonization (pyrolysis and carbonization of non volatile substances 200-650.degree. C.; and b) gasification of the pyrolytic residue at high temperature (650-850.degree. C.9) in the presence of limited quantities of an oxidant, such as water vapour, oxygen, etc. Said procedure is the most used at industrial scale. The main disadvantage resides in the gasification stage, since part of the carbon mass is also eliminated together with the pyrolyzed residue, due to the oxidation of the same.
The biological regeneration uses microorganisms which degrade the adsorbed substances.
In the regeneration with water vapour, the carbon is heated in the presence of water vapour, which acts as oxidant, degrading and destroying the retained compounds.
In the extraction with organic solvents, the carbon is contacted with an appropriate solvent, which dissolves the adsorbed substances.
The extraction with supercritical CO.sub.2, uses CO.sub.2 as solvent, at a temperature and a pressure over that of its critical point (31.1.degree. C. and 72 bar).
In the regeneration by wet oxidation, hot water in liquid condition is used (temperatures and pressure below critical point, 374.degree. C. and 215 bar), to which air is added (oxygen). The hot water and the oxygen dissolve, oxidize and destroy the adsorbed substances. The disadvantage of said method, lies in that the oxygen also oxidizes the carbon, especially if the temperature is high. Over 250.degree. C., the oxidation of the carbon is so rapid, that great losses of carbon are produced during the treatment.